Process of forming wood-fiber insulation board containing sulfine polymer, aldehyde and mineral acid and board thereof



United States Patent 3,332,835 PROCESS OF FORMING WOOD-FIBER INSULA- TION BOARD CONTAINING SULFINE POLY- MER, ALDEHYDE AND MINERAL ACID AND BOARD THEREOF Keith L. Smith, Charleston, W. Va., assignor to Union Carbide Corporation, a corporation of New York No Drawing. Filed Jan. 29, 1964, Ser. No. 341,112 11 Claims. (Cl. 162168) This invention relates to the production of wood-base construction and insulation board from wood-fiber pulp. More particularly, the invention relates to the incorporation in such board of minor amounts of certain substantially water-soluble sulfine polymers, alone or in combination with suitable aldehydes, or mixtures of such aldehydes and mineral acids, whereby enhanced dryand wet-strength, improved stiffness, and other desirable physical properties are obtained. The invention further comprehends the improved construction and insulation board produced in this manner.

Wood-fiber board is widely used as a construction material and is at present the most common low cost rigid insulation for general construction use. It is used in the form of panels ranging in thickness up to about an inch for rigid interior Wall insulation, as interior acoustical surfacing for ceilings, and, with a suitable surface coating, for wall sheathing. Processes used to produce such board are similar to the conventional paper forming process. Virgin or reclaimed groundwood is generally used and the wood-pulp spread on a screen or wire with dewatering being accomplished by gravity and by suction below the wire. The board is then squeezed or pressed by any of a variety of techniques, cut into panels of suitable size, and dried in an oven at an elevated temperature, generally from about 200 to 350 F.

The physical properties of commercial wood-fiber board are typically a result of a compromise between the conflicting requirements of insulation properties, tensile properties and cost. Since wood-fiber board, in common With paper products generally, retains only a small fraction of its dry strength when soaked in water the tensile strength and stiffness under conditions of high humidity or water saturation are of critical concern. Stiffness assumes special importance where the material is used for. ceiling tile or composite'roof deck-ceiling because of the tendency for sagging and warping to occur after prolonged periods of exposure to relatively high humidity levels. Heretofore, improvement in wood fiber board properties has been achieved either by subjecting the pulp slurry to prolonged beating or by the addition of starch in amounts of up to 3 to 4 percent. However, the former is unsatisfactory because of increased costs, decreased production rate as a result of increased water retention, and improvement in tensile properties only at the expense of a substantial increase in density and consequent reduction in insulation value; while the latter is undesirable because of the tendency for starch addition to substantially increase the drain time and water retention in the board on the wire and thereby decrease production rate and also because the board retains a pronounced susceptibility to moisture.

It is a primary object of this invention to provide an improved wood-fiber board having enhanced dry tensile strength, wet tensile strength, initial stiffness and apparent stiffness after continued exposure to high-moisture conditions. A further object of this invention is to provide an improved process for the production of wood-base construction and insulation board wherein the addition of minor amounts of additives provides enhanced tensile and other physical properties. A still further object of this ice invention is to provide additives to wood-fiber pulp which permit production of wood-fiber board at a faster rate, with less water retention at various stages in the manufacturing process, thereby reducing production cost and increasing the production capacity of board manufacturing equipment. Yet another object of the invention is to provide additives for wood-fiber board manufacture which greatly improve the physical properties of the wood-fiber board at low levels of add-on. Other objects and advantages of the invention will be apparent from consideration of the following detailed description together with the appended claims.

It has now been found that the disadvantages of the prior art methods of producing wood-base construction and insulation board, as hereinabove described, can be substantially overcome and a greatly improved board produced through the practice of the present invention which comprises applying to the wood-fiber pulp from which said board is formed a strength improving composition comprising a water-soluble polymer of an alpha-ethylenically unsaturated sulfine, i.e. a sulfonium compound possessing a terminal ethylenic unsaturation. While addition of said polymer alone results in a substantially improved prodnot, even greater improvement in the physical properties of wood-fiber board can be achieved by applying, in combination with such polymer, a minor amount of an aldehyde or, more preferably, a mixture of an aldehyde and a mineral acid as hereinafter described; and, accordingly, addition of said aldehyde or mixture of aldehyde and mineral acid is preferred in the practice of this invention.

Specifically, the sulfine polymers contemplated by this invention as treating agents for wood-fiber board include the homopolymers of the alpha-ethylenically unsaturated sulfines represented by the formula:

wherein R designates either a hydrogen atom or a methyl radical; R' designates an alkylene radical containing from 1 to about 4 carbon atoms and preferably from 2 to 3 carbon atoms, such radical more preferably separating the adjacent (in this instance oxygen and sulfur) atoms by a carbon chain containing at least 2 carbon atoms;-

pecially with at least one other copolymerizable monomeras, for instance, the alkylthioalkyl acrylates and methacrylates represented by the formula:

wherein R, R and R are as defined above, such as methylthiomethyl acrylate, methylthioethyl acrylate, ethylthioethyl acrylate, butylthioethyl acrylate, methylthiobutyl acrylate, methylthioethyl methacrylate, and the like; acrylamide and lower alkyl substituted acrylamides, such as rnethacrylamide and N,N-dimethylacrylamide; the vinyland the like; the vinyl alkanoates represented by the formula:

wherein R" is as defined above, such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pentanoate, and the like: the N-alkyl-N-vinylamides represented by the formula:

wherein each R" is independently selected as defined above, such as N-methyl-N-vinylacetamide, N-ethyl-N- vinylacetamide, N-butyl-N-vinylacetamide, N-methyl-N- vinylpropionamide, and the like; and the N-vinylpyrrolidones, such as N-vinyl-2-pyrrolidone; the amount of polymerized sulfine in the interpolymers being sufficient to assure the substantial and preferably complete water solubility of the interpolymers. Found to be particularly effective in this regard, are the interpolymers containing atv least 5 mole percent and preferably from about mole percent to about 99 mole percent of the sulfine in polymerized form on a theoretical monomer basis, the minimal amount of polymerized sulfine required to assure the water solubility of the interpolymers varying somewhat depending upon the particular comonomer(s) polymerized therewith.

The hereinabove described polymeric treating agents may be added directly to the dilute suspension of woodfiber pulp that is fed to the forming wire or, more preferably, the polymer may be dissolved in water and then added to the pulp. The treating agents may be added to the pulp either before or after it is beaten or otherwise agitated, but are preferably added before or at the beater if beating is desired. Substantial improvement in the physical properties of the wood-fiber board product has been found to result irrespective of the amount of beating the pulp is given, or whether it is beaten or not. Moreover, the improvement in the properties of wood-fiber board by use of the method of this invention is substantially independent of the pH level of the pulp slurry. As hereinbefore disclosed, it has been found that the polymeric treating agents of this invention substantially increase the Wet and dry strength, stiffness and stiffness retention of woodbase construction and insulation board comprised of wood fiber pulp. Furthermore, their use in the manner described herein reduces the water retention and increases the porosity of the board inthe forming operation as compared with methods heretofore known, thereby increasing production rate and production economy.

The polymeric treating agents of this invention can be produced by several different techniques. For instance, the alpha-ethylenically unsaturated sulfine represented above by Formula I can be obtained initially in monomeric form and subsequently polymerized by conventional processes forthe polymerization of alpha-ethylenically unsat- Jrated compounds either alone, so as to produce homopolyrners thereof, or together with one or more comonomers hereinabove described, so as to produce interpolymers thereof. When desired initially in monomeric form, the sulfinecan readily be obtained by reacting the corresponding alkylthioalkyl acrylate or methacrylate represented above by Formula II with an alkylating agent, viz, dimethyl sulfate. Reactions between a thio-ether and an alkylating agent are in general discussed, for instance, in Organic Chemistry, vol. I, 2nd ed., by H. Gilman, John Wiley and Sons, NY. (1948), page 867, such teachings being incorporated herein by reference. Concordant therewith, by way of illustration, the alkylation can be carried out by bringing the thio-ether and the alkylating agent into reactive admixture, in a suitable solvent or diluent if desired, and at a temperature of from about 25 C. or slightly lower, up to about C. to C., or slightly higher. In addition, a small amount of a conventional polymerization inhibitor, such as hydroquinone, or the like, is preferably incorporated in the reaction mixture. Moreover, the reaction is preferably carried out in a diluent which is a solvent for the thio-ether but a non-solvent for the resulting sulfine, such as benzene, isopropyl ether, etc. The sulfine product can then be separated and recovered in any convenient manner.

The polymeric treating agents of this invention can thereafter be obtained by conventional polymerization processes. Thus, for example, solution polymerization techniques can be utilized wherein an inert organic solvent solution of the sulfine alone, or in admixture with one or more comonomers, in proportions as hereinabove described, is contacted with a catalytic amount of a polymerization catalyst and maintained at a temperature at which polymerization will occur for a period of time suflicient to produce a polymer product. A particularly useful solvent which can be utilized in this connection is acetonitrile, although any other suitable inert organic solvent, such as acetone, N,N-dimethylformamide, dimethylsulfone, N,N-dimethylacetamide, ethylene carbonate, ethylene carbamate, gamma-butyrolactone, N-methyl-2- pyrrolidone, etc., can also be employed. Alternatively, bulk, suspension or emulsion polymerization techniques can also be used under otherwise similar reaction conditions, i.e., proportions, temperature, time, etc. Similarly, other diluents such as Water, benzene, toluene, xylene, hexane, heptane, etc., can also be used.

The catalysts most frequently employed in the polymerization reactions, and especially in connection with solution polymerization techniques, are the free-radical-type polymerization catalysts, such as the azo compounds, of which azo-2,2'-diis-obutyronitrile, dimethyl azo-2,2'-diisobutyrate, azo 2,2'-bis(2,4 dimethylvaleronitrile), azo- 2,2'-diisobutyramide, and the like, are typical. Other freeradical-type polymerization catalysts which can be employed are the peroxides, such as hydrogen peroxide, acetyl peroxide, benzoyl peroxide, peracetic acid, potassium persulfate, calcium percarbonate, etc. The catalyst is ordinarily incorporated in the polymerization reaction mixture in a concentration of from about 0.01 percent to about 5 percent or more by weight, and preferably from about 0.2 to about 2 percent by weight, based upon the total weight of monomer present, although any catalytic amount thereof can be utilized.

In general, the polymerization is carried out by contacting the monomers with the catalyst at a temperature of from about 10 C., or slightly lower, to about C., or slightly higher, accompanied by heating or cooling, as needed to maintain the temperature at the desired level. The reaction period to be employed will depend upon a variety of factors, such as the nature of the monomer(s), catalyst and/or diluent, the reaction temperature, etc., and can vary over a wide range. For instance, a suitable reaction period generally lies in the range of from about 1 to about 200 hours, but is not necessarily limited thereto. In addition, the polymerization can. be carried out under atmospheric, superatmospheric or subatmospheric pressures, as desired.

Upon completion of the polymerization reaction, the

polymer product can be recovered in any convenient manner, such as by coagulation, filtration, centrifugation, etc.

The reaction product can also be employed directly in many uses for the polymer product, obviating the recovery of the polymer per se.

In an alternative manner to the polymerization technique described above, the alkylation of the thio-ether producing the sulfine, and the polymerization of the monomer(s) can be carried out in one operation by incorporating the alkylating agent in a polymerization reaction mixture containing, as the polymerizable monomer(s), the thio-ether alone, or in admixture with at least one other member of the group of comonomers specifically defined above. In such a procedure, it is to be noted, the alkylating agent should be employed in a mole ratio of at least about 0.05 :1, preferably at least about 0.111, and more preferably at least about 0.25:1, up to about 5:1, or higher, with regard to the thio-ether. Moreover, when another comonomer is present, the alpha-ethylenically unsaturated thio-ether should be employed in an amount sufficient'to provide upon alkylation and polymerization, on a theoretical monomer basis, at least about 5 mole percent, and preferably at least about mole percent of a polymerized sulfine, based upon the total amount of polymerized monomers present in the resulting polymer. Such amount is readily determined by one skilled in the art in light of this disclosure. The polymerization reaction and the recovery of the resulting polymer, when desired, is carried out asotherwise described above.

The polymeric treating agents of this invention can also be prepared by reacting the alkylating agent with an initially formed polymer, i.e., either a homopoly-mer of the thio-ether, or a copolymer thereof with another alphaethylenically unsaturated comonomer as specifically defined above, the alkylation and initial polymerization reactions being carried out as otherwise described above. In such a procedure, the alkylation is preferably carried out in solution, suitable solvents being the same as those described above in connection with the polymerization reaction. The resulting polymer product can thereafter be recovered, when desired, by coagulation, filtration, centrifugation, or in any other convenient manner.

Itis preferred to add the above-described water-soluble polymers of alpha-ethylenically unsaturated sulfines to the wood-fiber pulp in combination with a suitable aldehyde and particularly preferred to add them in combination with a mixture of the aldehyde and a mineral acid. Addition of the aldehyde along with the sulfine polymer results in improved performance, i.e., the woodfiber board produced has even greater wet and dry strength, stiffness and stiffness retention. Moreover, addition of a mineral acid plus the aldehyde plus the sulfine polymer results in even greater improvement in these properties. On the other hand, addition of aldehydes or mineral acids alone to wood-fiber pulp does not result in any significant improvement in board properties. Thus, treatment of the wood-fiber pulp with the unique combination of sulfine polymer, aldehyde and mineral acid in accordance with this invention provides properties that cannot be obtained in any other way.

The suitable aldehydes for use in this invention are compounds of the general formula:

wherein X is selected from the group consisting of a formyl radical and an acetyl radical m is an integer of from 1 to 3, and n is an integer of from 0 to 1. Illustrative of the suitable aldehydes one can mention glyoxal, pyruvic aldehyde, succinaldehyde, glutaral dehyde, Z-hydroxyadipaldehyde, and the like.

' In a preferred embodiment of the present invention, a water-soluble mineral acid is added to the Wood-fiber pulp along with the sulfine polymer and the above-described aldehyde. To ensure that there is no deleterious effect on the food-fiber pulp, the mineral acid employed should preferably be a non-oxidizing mineral acid, i.e. a mineral acid which does not function'as an oxidizing agent. Particularly preferred mineral acids for the purpose of this invention are hydrochloric acid, sulfuric acid, sulfurous acid and phosphoric acid.

The strength improving compositions of this invention, whether composed of sulfine polymer alone, sulfine polymer plus aldehyde, or sulfine polymer plus aldehyde plus mineral acid, are added to the wood fiber pulp in minor amounts and preferably in the form of an aqueous solution. The invention contemplates construction and insulation board comprised of wood-fiber pulp and containing from about 0.05 percent to about 5 percent, more suitably from about 0.5 percent to about 2 percent, and prefer-ably from about 0.8 percent to about 1.2 percent, based on the weight of said pulp, of the strength improving composition. The said strength improving composition can contain '50 percent to 100 percent by weight of the normally solid, water soluble sulfine polymer hereinbefore described and 50 percent to 0 percent by weight of a mixture of an aldehyde of the formula given hereinabove and a mineral acid. Preferably, the strength improving composition is composed of 60 percent to percent by weight of the sulfine polymer and 40 percent to 5 percent by weight of the mixture of aldehyde and mineral acid. The said mixture can be composed of 80 percent to percent by weight of the aldehyde and 20 percent to 0 percent by weight of the mineral acid, more preferably 80 to 99 percent by weight of the aldehyde and 20 percent to 1 percent by weight of the minera acid. I

The strength improving compositions of this invention will provide enhanced properties with any of the woodfiber pulps that are employed in the manufacture of insulation board, but are particularly eliective with pulps that have not been given a high degree of chemical or mechanical refinement, e.g., groundwood, reclaimed groundwood, or semi-chemica pulps. The pulp should contain a substantial amount of its original lignin and/or hemicellulose content. The said strength improving compositions may be employed alone or in conjunction with other additives commonly incorporated in wood-fiber board, for example, materials functioning as sizes, Waterproofing agents, fire retardants, biological control agents and so forth. 1

The enhanced properties resulting from the incorporation of the strength improving compositions hereinbefore described in Wood-fiber pulp employed to produce construction and insulation board can be achieved with any drying schedule normally used in the manufacture of wood-fiber board. Thus, drying can be carried out at temperatures from about 200 F., or less, to about 350 F., or more, for periods of from about 2 hours to about 100 hours. While applicant does not wish to be bound by the consequences of any theory, it is believed that chemical interaction of the additives and the woodpulp occurs during drying and that the improvement in physical properties of the product board results from such chemical interaction.

The following examples are given to illustrate the invention, it being understood that these examples are not intended to be limiting of the invention but merely illusstrative thereof. In connection therewith the following definitions and descriptive material are provided.

By the term reduced viscosity as employed herein is meant the value obtained by dividing the specific viscosity of a polymer solution by the concentration of the polymer in the solution, the concentration being calculated in grams of polymer per 100 milliliters of solvent at a given temperature. The specific viscosity of the polymer solution is obtained. by dividing the difference bethe wood-fiber board was calculated using the approxi mate formula for the deflection of a cantilevered beam.

Example 1 tween the viscosity of the polymer solution and the vis- To a ten gallon glass-lined autoclave there were cosity of the solvent by the viscosity of the solvent. The charg Pounds of ceton1tr11e, 4.7 pounds of y reduced viscosity of a polymer is taken as a measure amide, Pounds of 2-me y -he hy1 acryla e, 2.7 of the molecular weight of the polymer, with a higher pounds of dimethyl sulfate, and 0.2 pound of acetyl perreduced viscosity indicating a higher molecular weight xid The au oclave was purged With nitrogen and polymer. Conversely a lower reduced viscosity indicates 10 h a d t 50 C. and after an inductioni of about a lower molecular weight polymer. In all cases, the re- 2 hours the Polymerization began as ihdleated y a e duced viscosity values set forth herein were determined P a u ris f ab ut 4 C. The polymerization reaction at a concentration of 0.2 grams of polymer per 100 milli- Was allowed to Pfeeeed for an addltlonal 4 after liters of solvent and at a temperature of 30 C., using which tiIhe the autoclave was cooled and the Polymer a 0.5 molar aqueous sodium actate solution as the sol- Suspension dumped into a Centrifuge- After Washing the vent, unless otherwise specifically mentioned. As so P y three times With y acetone drying in a measured, the polymeric treating agents of this inven- Vacuum dryer for about 24 hours at C, There Were tion generally have a reduced viscosity of from about recovered, in the form of a White free flowing Powder, 0.5 to about 5, and most frequently from about 2 to about aPPYOXimately Pounds of a P y composed of 4. The polymers of higher molecular weight provide the approximately 48 Percent y Weight of polymerized gratest increase in both wet and dry tensile strengths of aefyloXyethyl)dimethylsulfoniu-m methylsulfate and 52 the Wood-fiber board and are thus preferred in the prac- Percent y Weight polymerized 'y This P ytice of this invention mer had a reduced viscosity in 0.5 molar sodium bisul- Wet and dry tensile strength values reported herein fite of3eowere determined in accordance with methods outlined In a Similar manner, P y p y in ASTM Dl037-60T, Evaluating the Properties of placing the aerylamide With vinyl acetate or y Wood-Base and Particle Panel Materials. The dried Nwinylaeetamide Y -PY ethy1 board samples were brought to equilibrium under con- White or y y 'y stant conditions at 23 C. and 50 percent relative hu- 7 Examples 2-7 midity Wet strength samples were first soalsed for 16 A woodfiber pulp containing 598 percent water as 3 9$ under a 1 lllch h of water 3 taken from the grinding mill was partially shredded by was determmed the bone'dry con usmg hand and then added to distilled Water to form a slurry f samplescontaining 1 weight percent pulp on a bone dry basis. Stiffness measurements were made wlth Speclany, The slurry was dispersed in a laboratory Osterizer running P aPPaFatuS- the proceclure employed f at top speed for a period of one minute and then 200 35031 363 3 23 sst i g g zzg i ng f fg afl g' grams were poured into a laboratory Buchner funnel fitted eteted trenenetent ehenthen Using the weight per unit iifin teii ilii eiiii ii siliili eiii a fiibiei gtf fil iii lengih and thickhess for eachsam'plee e length of the 40 slurry was permitted to drain under low vacuum and then cahhlevered Section of each Plece was l PP Y the wood-fiber pulp mat was removed from the funnel, maxim m fiber stress of pounds per square lnch. 'Ijhe sandwiched between stainless steel screens and pressed board samples were equilibrated for a 48-hour period f 2 mmutes under a 10 pound i h The mat was lwifh the 2tgst cgambcer in da constant tlernpe-ratur room then removed and baked in a forced draft oven for 16 ed at .0: .2 an with distil ed water in the e bottom of the chamber and the air within recirculated 2335255 3 1 ligjg g ffigli? a wood fiber board product through a diffuser placed in the water. Test conditions Physical properties of wood-fiber board samples were thus ZIP-Preaching Water Saturation at pared in the above-described manner are summarized in ing the equilibration period the cantilevered p n of Table I below. Where it is indicated that a strength imthe strip was supported in a horizontal plane by a second 50 proving composition was added to the pulp, th m aeellfately-pesltlolled plastle block- Deflection 0f the nents of the composition were dissolved in water and then cantilevered end of the test strip was meatured with a added to the pulp slurry prior to dispersion in the Oster cathetometer at frequent intervals. Apparent stiffness of izer.

TABLE I Board Strength Concentration Dry Ex. Additive (Weight Board N 0. Percent) Dry Wet Density Tensile Tensile (g./cc.) (p.s.i.) (p.s.i.)

None None 19. 9 5. 6 0.1527 A- 0. 5 41. 2 14. 5 0.1623 A 1.0 48.7 15.4 o. 1660 B. 1. 0 43. 5 3. 0 0.1579 A+Glyoxal+HG 1.0+0.1+0.01 68.4 19.4 0.1749 A+Glyoxal+HC1 1 0+0. 5+0. 05 59.5 17.3 0.1700

B=Polymer comprised of 25 mole percent polymerized (2-acryioxyethyl) dimethylsulfonium methylsulfate and mole percent polymerized acrylamide.

9 Consideration of the results presented in Table I above shows that both wetand dry-strength of the wood fiber board is greatly increased by the addition of a sulfine polymer typical of those disclosed herein and that even 10 percent to about percent, based on the weight of said pulp, of a strength improving composition composed of (1) 60 percent to 95 percent by weight of a normally solid, water soluble, sulfine polymer selected from the group greater improvement in these properties results by com- 5 consisting of (a) homopolymers of an alpha-ethylenically bination of an aldehyde and a mineral acid typical of unsaturated sulfine of the formula: those disclosed herein with the sulfine polymer. R O

Example 8 oHi=-("J-o-R' s+ anisot- Wood-fiber board samples were prepared in a similar 10 Ha manner to that descl'lbed 1n P Q and wherein R is selected from the group consisting of hydrodry'strength values determmed for Venous addl' gen and the methyl radical, R is an alkylene radical of tlves- Results are reported In Table H belowfrom 1 to 4 carbon atoms, and R" is an alkyl radical of TABLE II from 1 to 4 carbon atoms, and (b) interpolymers of said sulfiine with at least one coplymerizable monomer selected 0 tr Board Strength from the group consisting of (i) the alkylthioalkyloncen 9. ion Additive (weight Percent), Dry Tensile Wet Tensile acrylates and methacrylates of the formula.

(p.s.i. (p.s.i.) R H 23.1 5.63 g-g 2-3? wherein R, R and R" are as defined above, (ii) acryl- G oxal 1. 0'+0.1 33:9 1215 amide and met-hacrylamide, (iii) the alkyl and cyano- A'lmWXaHHm alkyl acrylates and methacrylates of the formula:

1 Based on bone dry weight of wood pulp. O A=Polymer comprised of 10 mole percent polymerized (2-acryloxy- L n/ ethyl) dirnethylsulfonium methylsulfate and 90 mole percent polymerized D y de (reduced y= wherein R is as defined above, R is an alkylene radical In this particular test series, the tensile strengths did of from carbon atoms, and Y is selectedtrom t not reach as high levels as those shown in Examples 2-7 t} COIlSlStlIlg of hydrogen and the cyallo radical, but performance differences within the series are evident t e v yl al auoates of the formula: and indicate that the combination of sulfine polymer, aldehyde and mineral acrd is uniquely effective in improving |l the tensile properties of wood-fiber board.

wherein R" is as defined above, (v) the N-alkyl-N-vinyl- Example 9 alkylamides of the formula: Wood-fiber board samples were prepared in a similar 0 1, manner to that described in Examples 2-7 above and stiifl ness values were determined in the manner hereinbefore described for various additives. Results of this series of tests are reported in Table III below. wherein each R" is independently selected as defined TABLE III Apparent Stifiness oi Wood-Fiber Board (p.s.i.) Additive Concentration (Weight Percent) Initial After One Alter One Hour Week None 1, 335 311 107 A 1. 0 2, 973 see 192 A+Glyoxal+HCl 1.0+0. 01+0. 002 3,273 629 19s 1 Based on bone dry weight of wood pulp.

Results presented in Table III above indicate that the addition of a sulfine polymer typical of those disclosed herein to wood-fiber board greatly increases its initial and apparent stifiness and that even greater improvement in this physical property is achieved by addition of an aldehyde and mineral acid typical of those disclosed herein along with the sulfine polymer.

Various changes and modifications can be made in practicing the present invention without departing from the spirit and scope thereof, and therefor it is intended to include within the scope of the appended claims all such modifications and variations as may be apparent to those skilled in the art from the description and illustrative examples given herein.

What is claimed is: t I 1.- A wood-base construction and insulation board comprised of wood-fiber pulp and containing from about 0.05

above, (vi) N-vinylpyrrolidone, and (vii) vinylbenzene, said interpolymers containing in polymerized form and on a theoretical monomer basis from about 10 to about 99 mole percent of said alpha-ethyleuically unsaturated sulfine, and (2) 40 percent to 5 percent by weight of a mixture of to 99 percent by weight of an aldehyde of the general formula:

wherein X is selected from the group consisting of a formyl radical and an acetyl radical, m is an integer of from 1 to 3, andn is an integer of from 0 to 1, and 20 percent to 1 percent by weight of a mineral acid selected from the group consisting of hydrochloric acid, sulfuric acid, sulfurous acid and phosphoric acid.

2. The wood-base construction and insulation board of claim 1 wherein said aldehyde is glyoxal.

3. The wood-base construction and insulation board of claim 1 wherein said mineral acid is hydrochloric acid.

4. A wood-base construction and insulation board comprised of wood-fiber pulp and containing from about 0.5 percent to about 2 percent, based on the weight of said pulp, of a strength improving composition composed of (1) 60 percent to 95 percent by weight of a normally solid, water soluble, sulfine polymer selected from the group consisting of (a) homopolymers of an alpha-ethylenically unsaturated sulfine of the formula:

CH3 S 04' I? OH-,=CCR'SR wherein R, R and R" are as defined above, (ii) acrylamide and methacrylamide, (iii) the alkyl and cyanoalkyl acrylates and methacrylates of the formula:

f it CHFCCO-RY wherein R is as defined above, R is an alkylene radical of from 1 to 10 carbon atoms, and Y is selected from the group consisting of hydrogen and the cyano radical, (iv) the vinyl alkanoates of the formula:

wherein R" is as defined above, (v) the N-alkyl-N-vinylalkylamides of the formula:

CH=CH2 wherein each R" is independently selected as defined above (vi) N-vinylpyrrolidone, and (vii) vinylbenzene, said interpolymers containing in polymerized form and on a theoretical monomer basis from about 10 to about 99 mole percent of said alpha-ethylenically unsaturated sulfine, and (2) 40 percent to 5 percent by weight of a mixture of 80 to 99 percent by weight glyoxal and 20 percent to 1 percent by weight hydrochloric acid.

5. A wood-base construction and insulation board comprised of wood-fiber pulp and containing from about 0.5 percent to about 2 percent, based on the weight of said pulp, of a strength improving composition composed of (1) 60 percent to 95 percent by weight of a normally solid, water soluble copolymer of (2-acryloxyethyl)dimethylsulfonium methylsulfate and acrylamide, said copolymer containing in polymerized form and on a theoretical monomer basis from about to about 99 mole percent of said (2-acryloxyethyl)dimethylsulfonium methylsulfate, and (2) 40 percent to 5 percent by weight of a mixture of 80 to 99 percent by weight glyoxal and 20 to 1 percent by weight hydrochloric acid.

6. A wood-base construction and insulation board comprised of wood-fiber pulp and containing about 0.8 percent to about 1.2 percent, based on the weight of said pulp, of a strength improving composition composed of about 90 percent by weight of a normally solid, water soluble copolymer of (2-acryloxyethyl)dimethylsulfonium methylsulfate and acrylamide, said copolymer containing in polymerized form and on a theoretical monomer basis about 10 mole percent of said (2-acryloxyethyl) dimethylsulfonium methylsulfate, and about 10 percent by weight of a mixture of about 99 percent by weight glyoxal and about 1 percent by weight hydrochloric acid.

7. In a process for the production of a wood-base construction and insulation board comprised of wood-fiber pulp, the improvement which comprises applying to said Wood-fiber pulp in aqueous suspension about 0.05 percent to about 5 percent, based on the weight of said pulp, of a strength improving additive composition composed of (1) 60 percent to percent 'by weight of a normally solid, Water soluble, sulfine polymer selected from the group consisting of (a) homopolymers of an alphaethylenically unsaturated sulfine of the formula:

wherein R is selected from the group consisting of hydrogen and the methyl radical, R is an alkylene radical of from 1 to 4 carbon atoms, and R" is an alkyl radical of from 1 to 4 carbon atoms, and (b) interpolymers of said sulfine with at last one copolymerizable monomer selected from the group consisting of (i) the alkylthioalkylacrylates and methacrylates of the formula:

wherein R, R and R" are as defined above, (ii) acrylamide and methacrylamide, (iii) the alkyl and cyanoalkyl acrylates and methacrylates of the formula:

wherein R is as defined above, R is an alkylene radical of from 1 to 10 carbon atoms, and Y is selected from the group consisting of hydrogen and the cyano radical, (iv) the vinyl alkanoates of the formula:

if RCOCH=CH wherein R" is as defined above, (v) the N-alkyl-N-vinylalkylamides of the formula:

R"C N OH=CH2 OH (H) X-CmHzm(( 3H ,r-C-H wherein X is selected from the group consisting of a formyl radical and an acetyl radical, m is an integer of from 1 to 3, and n is an integer of from 0 to 1, and 20 percent to 1 percent by weight of a mineral acid selected from the group consisting of hydrochloric acid, sulfuric acid, sulfurous acid and phosphoric acid.

8. The process of claim 7 wherein said aldehyde is glyoxal.

9. The process of claim 7 wherein said mineral acid is hydrochloric acid.

10. In a process for the production of a wood-base construction and insulation board comprised of woodfiber pulp, the improvement which comprises applying to said wood-fiber pulp in aqueous suspension about 0.5

percent to about 2 percent, based on the weight of said pulp, of a strength improving composition comprised of (l) 60 percent to 95 percent by weight of a normally solid, water soluble copolymer of (2-acry1oxyethyl)dimethylsulfonium methylsulfate and acrylamide, said copolymer containing in polymerized form and on a theoretical monomer basis from about 10 to about 99 mole percent of said (Z-acryloxyethyl)dimethylsulfonium methylsulfate, and (2) 40 percent to 5 percent by weight of a mixture of 80 to 99 percent by weight glyoxal and 20 to 1 percent by weight hydrochloric acid.

11. In a process for the production of a wood-base construction and insulation board comprised of wood-fiber pulp, the improvement which comprises applying to said wood-fiber pulp in aqueous suspension about 0.8 percent to about 1.2 percent, based on the weight of said pulp, of a strength improving composition composed of about 90 percent by weight of a normally solid, water soluble copolymer of (Z-acryloxyethyl)dimethylsulfonium methylsulfate and acrylamide, said copolymer containing in polymerized form and on a theoretical monomer basis about 10 mole percent of said (Z-acryloxyethyl)dimethylsulfonium methylsulfate, and about 10 percent by weight of a mixture of about 99 percent by weight glyoxal and about 1 percent by Weight hydrochloric acid.

References Cited UNITED STATES PATENTS 2,285,490 6/1942 Broderick 162158 X 3,096,228 7/1963 Day et a1. 162158 X 3,130,117 4/1964 Humiston et a1 162168 3,207,656 9/1965 Eldred et al. 162168 S. LEON BASHORE, Primary Examiner. 

1. A WOOD-BASE CONSTRUCTION AND INSULATION BOARD COMPRISED OF WOOD-FIBER PULP AND CONTAINING FROM ABOUT 0.05 PERCENT TO ABOUT 5 PERCENT, BASED ON THE WEIGHT OF SAID PULP, OF A STRENGTH IMPROVING COMPOSITION COMPOSED OF (1) 60 PERCENT TO 95 PERCENT BY WEIGHT OF A NORMALLY SOLID, WATER SOLUBLE, SULFINE POLYMER SELECTED FROM THE GROUP CONSISTING OF (A) HOMOPOLYMERS OF AN ALPHA-ETHYLENICALLY UNSATURATED SULFINE OF THE FORMULA: 